1. Field of the Invention
The present invention relates to a steering system for a motor vehicle.
2. Description of the Relevant Art
There is known an automotive steering system for steering both front and rear wheels of an automobile as disclosed in British Patent Publication No. 2161437A. In such a steering system, no wheel is available as a reference for adjusting wheel alignment of all four wheels since the front and rear wheels are steerable. Therefore, it has been difficult to adjust the relationship between degrees of toeing of front and rear wheels and the relationship between the degrees of toeing of right and left wheels, and hence it has been time-consuming and expensive to make such adjustments.
British Patent Publication No. 2151567A and Japanese Laid-Open Patent Publication No. 58-97565 disclose steering systems for steering both front and rear wheels on motor vehicles. In the disclosed steering systems, the output shaft of a front wheel steering device and the input shaft of a rear wheel steering device are interconnected by a linkage shaft, and a pinion is rotatably fitted over an eccentric shaft on the input shaft. The pinion has an integral eccentric member engaged by a joint member by which rear wheel tie rods are coupled to each other, the pinion being held in mesh with a fixed internal ring gear.
The disclosed systems are advantageous for the following reasons: The maximum steering angle of the rear wheels is larger when the rear wheels are steered in a direction opposite to that in which the front wheels are steered than when the rear wheels are steered in the same direction as that in which the front wheels are steered. Therefore, the steering system can provide good maneuvering response primarily in a high speed range of travel during which the automobile is usually steered, if at all, only in a relatively small angle range. On the other hand, in a low speed range during which the steering wheel is frequently turned in a relatively large angle range, the automobile can make smaller turns.
One problem of the conventional steering systems is that since the pinion can freely revolve within the ring gear through several turns, it is difficult to establish the neutral steering position of the rear wheel steering device when it is assembled or serviced.